diff --git a/direct/src/dcparser/dcClass.cxx b/direct/src/dcparser/dcClass.cxx
index 2df80967fc..762b8573c5 100644
--- a/direct/src/dcparser/dcClass.cxx
+++ b/direct/src/dcparser/dcClass.cxx
@@ -864,6 +864,8 @@ ai_format_generate(PyObject *distobj, int do_id,
         return Datagram();
       }
 
+      packer.raw_pack_uint16(field->get_number());
+
       packer.begin_pack(field);
       if (!pack_required_field(packer, distobj, field)) {
         return Datagram();